Series/parallel connected single phase power transformer

ABSTRACT

An improved single phase power transformer having a three-legged magnetizable stacked core is disclosed. Two half-size outer core legs are parallel to and are spaced apart from a full-size central leg. Coil windings are located on the central leg of the transformer core only. High and low voltage windings are in an interleaved relationship, with the lowest potential portion of the high voltage coil winding adjacent the central leg of the transformer core. High voltage coil windings are connected in series and low voltage coil windings are connected in parallel.

United States Patent [191 Manimalethu [451 July 15, 1975 1SERIES/PARALLEL CONNECTED SINGLE PHASE POWER TRANSFORMER [75] Inventor:Abraham I. Manimalethu, Peru,

Mass.

[73] Assignee: General Electric Company, New

York, NY.

[22] Filed: June 3, 1974 [21] Appl. No.: 475,564

[52] US. Cl. 336/183 [51] Int. Cl. IIOIF 27/28 [58] Field of Search336/180, 182, 183, 145, 336/146, 147, 170

[56] References Cited UNITED STATES PATENTS 1,652,911 12/1927 Sclater336/183 1,979,096 10/1934 Cahall.... 336/183 X 2,680,218 6/1954 Keroes336/183 X 2,713,667 7/1955 Schwennesen 336/183 FOREIGN PATENTS ORAPPLICATIONS 925,599 3/1947 France 336/183 695,222 8/1953 United Kingdom336/183 Primary Examiner-Thomas J. Kozma Attorney, Agent, or Firm-JohnJ. Kelleher [57] ABSTRACT An improved single phase power transformerhaving a three-legged magnetizable stacked core is disclosed. Twohalf-size outer core legs are parallel to and are spaced apart from afull-size central leg. Coil windings are located on the central leg ofthe transformer core only. High and low voltage windings are in aninterleaved relationship, with the lowest potential portion of the highvoltage coil winding adjacent the central leg of the transformer core.High voltage coil windings are connected in series and low voltage coilwindings are connected in parallel.

6 Claims, 3 Drawing Figures SERIES/PARALLEL CONNECTED SINGLE PHASE POWERTRANSFORMER BACKGROUND OF THE INVENTION My invention relates, ingeneral, to electrical power transformers and more particularly tosingle phase power transformers of the three-legged stacked core type,said core having coil windings on one leg only.

Conventional power transformers of the single phase type havetransformer cores of the two-legged or fourlegged stacked core type withcoil windings on two legs of the transformer core. High voltage and lowvoltage windings are included in each coil of such transformers withcoil windings subjected to the same working voltage being connected inparallel. These types of single phase power transformers have severalinherent disadvantages. The major disadvantage in such transformerdesigns is that excessive amounts of core steel must be used. Anotherdisadvantage is that such designs are relatively complex in that twoseparate coils are required and lengthy coil winding connections arerequired between coils. The aforementioned disadvantages results in ahigher cost, less reliable transformer than one that does not have suchdisadvantages.

In order to avoid these and other disadvantages, it would be desirableto provide a single phase power transformer that would significantlyreduce the amount of core steel required to fabricate sameas well asreduce costs and increase reliability.

Accordingly, it is an object of my invention to provide a single phasepower transformer that is less costly to build than single phase powertransformers utilizing a two-coil design and having two or moretransformer core legs.

Another object of my invention is to provide a single phase powertransformer that is more reliable than a single phase power transformerutilizing a two-coil design.

Still another object of my invention is to provide a single phase powertransformer that will minimize the length of the connections requiredbetween coil windings.

SUMMARY OF THE INVENTION An improved single phase power transformer isdisclosed that utilizes a single coil mounted on one leg of athree-legged transformer core of the stacked type. The present inventionis a single phase power transformer that has a three-legged magnetizablestacked core with two half-size outer legs parallel to and spaced apartfrom a full-size central leg. Coil windings in the shape of hollowcylinders, concentric with each other, are positioned around the centralleg of the transformer core only, such that the longitudinal centralaxes of the just mentioned coil windings are concentric with thelongitudinal central axis of said central leg. High and low voltagewindings are assembled such that they are in an interleaved relationshipwith each other, and the low potential winding portion of the highvoltage coil windings is adjacent the central leg of the transformercore. The high voltage coil windings are connected in series and lowvoltage coil windings are connected in parallel.

The invention. which is sought to be protected, will beparticularlypointed out and distinctly claimed in the claims appendedthereto. However, it is believed that this invention and the manner inwhich its objects and vention.

advantages are obtained. as well as other objects and advantagesthereof, will be more readily understood by reference to the followingdetailed description of the preferred embodiment thereof, particularly'when considered in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERREDEMBODIMENT Referring now to the drawings wherein like numerals are usedto indicate like parts throughout. in FIG. 1 the most pertinent portionsof single phase power transformer 12 of the present invention aredepicted. Transformer core 14, of the stacked type, having outer legs 16and 18 and central leg 20 is shown supported by clamping structure 22.Transformer housing 24 enclosing transformer core 14 is shown inphantom. Coil 26, the only coil in transformer 12, is shown encirclingcentral leg 20 of transformer core 14. Coil 26 consists of four coilwindings which are best pictured in FIG. 2.

FIG. 2 is a horizontal cross-sectional view taken along the line 22 inFIG. I. In FIG. 2 cross-sections of coil windings 28, 30, 32 and 34 ofcoil 26 are illustrated. Coil windings 28, 30, 32 and 34 are in theshape of hollow cylinders, are generally concentric with each other andwith the longitudinal axis of central leg mem ber 20. In addition, FIG.2 shows a horizontal crosssectional view of outer core legs 16 and 18and central core leg 20. The cross-sectional area of each outer core leg16 and 18 is approximately equal to one-half the cross-sectional area ofcentral leg 20.

Referring now to FIG. 3- where a shcematic diagram of the coil windingsand coil connections of coil 26 is illustrated. Coil windings 28, 30 32and 34 are central coil leg 20 are in the same relative relationship asthat depicted in FIG. 2. Coil winding 28 is a two terminal relativelyhigh voltage, layer winding and is located immediately adjacent centralcoil leg 20. The circular cross-sectional shape of the hollow centralportion of coil winding 28 conforms to the generally circularcross-sectional shape of central core leg 20. Coil winding 30 is a twoterminal relatively low voltage, helical winding that is immediatelyadjacent to and external of coil winding 28. Coil winding 32 is a twoterminal, relatively high voltage layer winding that is immediatelyadjacent and external of coil winding 30. Coil winding 34 is a twoterminal, relatively low voltage layer winding that is immediatelyadjacent and external of coil winding 32.

The higher voltage coil windings of the transformer of the presentinvention are labeled wih the letter H and the lower voltage coilwindings of the transformer of the present invention are labeled withthe letter X.

One end of high voltage 32 is connected to one end of coil winding 28 inan electrical series-aiding circuit relationship by electricalconnection 36. The remaining end of high voltage coil winding 32 is, forreference, designated H1 and is for connection to a high potentialterminal. The remaining end of high voltage coil winding 28 is, forreference, labeled H2 and is for connec' tion to a low potentialterminal. The terms high potential terminal and low potential terminalin this context mean high and low potential terminals with respect toone another.

One end of coil is connected to the end of coil 34 having the samepolarity as coil 30 by electrical connection 38. The remaining end ofcoil 30 is connected to the remaining end of coil 34 by electricalconnection 40. Electrical connection 38 is, for reference, labeled X1and electrical connection 40, for reference, is labeled X2. X1 is forconnection to a high potential terminal relative to X2 and X2 is forconnection to a low potential terminal relative to X1.

What has been described is a single phase power transformer that canhandle the same amount of power as previous designs but requiressignificantly less core steel, is less complex, more reliable and lesscostly to build than previous designs.

GENERAL CONSIDERATIONS l have discovered that if the reactance of atransformer coil is acccurately calculated it is possible to construct asingle phase power transformer such as that described in the preferredembodiment. In such a transformer, current necessarily divides in asubstantially uneven manner in the low voltage windings. If thereactance is not calculated to a fairly accurate degree, current in thelow voltage windings will divide such that excessive current will passthrough one of the low voltage windings causing the winding to fail.Computer programs have been available for several years for calculatingthe reactance of transformer coils to within three percent which isadequate for a transformer design'such as that described in thepreferred embodiment.

The transformer of the type described herein is commonly known as avoltage step-up power transformer. However, my invention would applyequally well to a voltage step-down power transformer. In such a voltagestep-up transformer the output voltage is significantly higher than theinput voltage. Coil 26 of the transformer of the type described hereinhas four coil windings designated 28, 39, 32 and 34. Coil windings 28and 32 form the relatively high voltage winding portion of coil 26 andcoil windings 30 and 34 form the relatively low voltage winding portionof coil 26.

As previously stated, the letter H is associated with the high voltagewindings and the letter X is associated with the low voltage windings.High voltage and low voltage in this sense is with respect to the highvoltage and low voltage windings in the transformer coil. A high voltageor low voltage reference terminal within either of the high voltagewindings or low voltage windings is terminology that is used herein todistinguish one end of a particular coil winding or windings fromanother and does not mean that the voltage at a particular terminalremains constant. XI and x2 are the high and low voltage referenceterminals respectively, for the low voltage windings which are labeledX. H1 and H2 are the high and low voltage reference terminalsrespectively, for the high voltage windings which are labeled H.

High voltage and low voltge windings of the present invention areinterleaved with respect to one another. That is to say a high voltagecoil winding is located between low voltage coil windings and a lowvoltage coil winding is located between high voltage coil windingsthroughout the entire coil except for the innermost and outermost coilwindings. High voltage and low voltage windings are never locatedimmediately adjacent one another.

In the preferred embodiment coil windings of the layer type have beenutilized. As a general. rule, layer type coil windings are used in veryhigh voltage applications. However, in those applications where moderatevalues of voltage will be encountered, disc windings may be substitutedfor layer windings if such a substitution is compatible with the desiredelectrical characteristics.

The terms layer, helical and disc are used herein to describe particularwell known types of coil windings and are among the most common types oftransformer coil windings in present use in the transformer art. Thisbeing so. no description of these windings, other than their names, isincluded herein.

It sill be apparent to those skilled in the art from the foregoingdescription of my invention that various improvements and modificationsmay be made in it without departing from the true scope of theinvention. Accordingly, it is my intention to encompass within the scopeof the appended claims the true limits and spirit of my invention.

I claim:

I. In a single phase electrical power transformer of the type having amagnetizable three-legged stacked core, said core having a central legand spacedapart outer legs parallel to said central leg, thecrosssectional area of each of said outer legs being approximatelyone-half the cross-sectional area of said central leg, the improvementcomprising:

a. a coil, including a plurality of hollow and generally cylindricalshaped alternating interleaved high voltage and low voltage windings,the longitudinal axes of said windings being generally concentric witheach other and with the longitudinal axes of said central leg of saidtransformer core. having one of said high voltage windings immediatelyadjacent said central leg;

. means connecting said low voltage windings in parallel; and

c. means connecting said high voltage windings in series; sequentiallyfrom the innermost to the outermost high voltage windings.

2. A single phase electrical power transformer as defined in claim 1wherein said coil consists of two high oltage windings and two lowvoltage windings.

3. A single phase electrical power transformer as defined in claim 2wherein said high voltage windings are of the layer type, the lowvoltage windings between high voltage windings is of the helical typeand the remaining low voltage winding is of the layer type.

4. A single phase electrical power transformer as defined in claim 2wherein said high voltage windings are of the layer type. the lowvoltage windings between high voltage windings is of the helical typeand the remaining low voltage winding is of the disc type.

5. A single phase electrical power transformer as defined in claim 2wherein said high voltage windings are of the disc type. the low voltagewinding between high 3 ,8 9 5 ,3 3 5 5 6 voltage windings of the helicaltype and the remaining of the disc type, the low voltage winding betweenthe low voltage winding is of the layer type. high voltage windings isof the helical type and the re- 6. A single phase electrical powertransformer as demaining low voltage winding is of the disc type. finedin claim 2 wherein said high voltage windings are LII

1. In a single phase electrical power transformer of the type having amagnetizable three-legged stacked core, said core having a central legand spaced-apart outer legs parallel to said central leg, thecross-sectional area of each of said outer legs being approximatelyone-half the cross-sectional area of said central leg, the improvementcomprising: a. a coil, including a plurality of hollow and generallycylindrical shaped alternating interleaved high voltage and low voltagewindings, the longitudinal axes of said windings being generallyconcentric with each other and with the longitudinal axes of saidcentral leg of said transformer core, having one of said high voltagewindings immediately adjacent said central leg; b. means connecting saidlow voltage windings in parallel; and c. means connecting said highvoltage windings in series, sequentially from the innermost to theoutermost high voltage windings.
 2. A single phase electrical powertransformer as defined in claim 1 wherein said coil consists of two highvoltage windings and two low voltage windings.
 3. A single phaseelectrical power transformer as defined in claim 2 wherein said highvoltage windings are of the layer type, the low voltage windings betweenhigh voltage windings is of the helical type and the remaining lowvoltage winding is of the layer type.
 4. A single phase electrical powertransformer as defined in claim 2 wherein said high voltage windings areof the layer type, the low voltage windings between high voltagewindings is of the helical type and the remaining low voltage winding isof the disc type.
 5. A single phase electrical power transformer asdefined in claim 2 wherein said high voltage windings are of the disctype, the low voltage winding between high voltage windings of thehelical type and the remaining low voltage winding is of the layer type.6. A single phase electrical power transformer as defined in claim 2wherein said high voltage windings are of the disc type, the low voltagewinding between the high voltage windings is of the helical type and theremaining low voltage winding is of the disc type.